Construction of joint portion of semi-submerged marine structure

ABSTRACT

The construction of a joint portion between a column and a bracing in a semi-submerged marine structure which consists of a platform, a column, a submerged body and a bracing to which the column is joined. The bracing consists of a portion having a small cross-sectional area, a tapering portion the cross-sectional area of which increases gradually toward a free end of the bracing, and a free end portion having a larger cross-sectional area. In a joint portion between the column and bracing, the portion of the bracing which has a larger cross-sectional area is in the interior of the column. If the tapering portion of the bracing is welded to the outer plate of the column, the stress in the joint portion can be dispersed into the outer plate and the same portion of the bracing.

FIELD OF ART

The present invention relates to a construction of a joint portion of asemi-submerged marine structure.

BACKGROUND ART

Semi-submerged marine structures generally have such a structure inwhich a plurality of columns having their respective upper portionprojecting above water surface are built on each of a plurality ofsubmerged bodies held in water and, while a platform is supported on andby all the columns, correspondingly located columns on respectivesubmerged bodies are supported in pairs by bracings.

Then, according to the prior art, the bracing is secured with itsportion having a larger cross-sectional area to the column in a mannersuch that a connection portion of the bracing at which the portionhaving a larger cross-sectional area and a tapering portion areconnected to each other is disposed outside the column, so that theproblem is encountered that stress concentrates at the connectionportion to produce cracking therein.

The present invention aims at avoiding the concentration of stress atthe connection portion in or of the bracings.

DISCLOSURE OF THE INVENTION

Thus, the present invention provides a construction of a joint portionin or of a semi-submerged marine structure in which a plurality ofcolumns having their respective upper portion projecting above watersurface are built on each of a plurality of submerged bodies held inwater and, while a platform is supported on and by all the columns,correspondingly located columns on respective submerged bodies aresupported in pairs by bracings, characterized in that a tapering portionthe cross-sectional area of which increases gradually toward a forwardend of the bracing, provided at an end of a portion of the bracing whichhas a smaller cross-sectional area, is secured to an outer plate of thecolumn in a manner such that a connection portion of the taperingportion and a portion of the bracing having a larger cross-sectionalarea is disposed in the interior of the column.

Attributable to this construction, according to the present inventionthe concentration of stress in the connection portion at which thetapering portion and the portion having a larger cross-sectional area ofthe bracing are connected together can be avoided.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view, partly in section, showing an example of theconstruction of a joint portion in or of a semi-submerged marinestructure pertaining to the present invention;

FIGS. 2 to 12 are plan views, partly in section, respectively showinganother example of the construction of a joint portion in or of asemi-submerged marine structure pertaining to the present invention;

FIG. 13 shows a front view of a semi-submerged marine structure of theprior art; and

FIG. 14 shows a sectional view, taken on line A--A in FIG. 13.

BEST MODE FOR THE CARRYING-OUT OF THE INVENTION

Generally, semi-submerged marine structures such as the one shown at 1have such a structure in which a plurality of columns 3 having theirrespective upper portion projecting above a water surface W are built oneach of a plurality of submerged bodies 2 held in water and, while aplatform 4 is supported on and by all the columns 3, the correspondinglylocated columns 3 and 3 on the submerged bodies are supported in pairsby bracings 5.

Then, according to the prior art, as illustrated in FIG. 14 the bracing5 is secured with its portion having a larger cross-sectional area, 6,to an outer plate 11 of the column 3 in a manner such that a connectionportion 8 of the bracing 5 at which the portion having a largercross-sectional area 6 and a tapering portion 7 are connected to eachother is disposed outside the column 3, so that the problem isencountered that stress tends to concentrate at the connection portion 8to produce cracking in this portion.

The present invention, which has for its object to cancel theabove-indicated problem in the prior art, is possessed of the followingstructural features.

FIG. 1 shows a construction of a joint portion in a semi-submergedmarine structure according to the present invention, and as shown, thebracing 5 comprises a portion having a smaller cross-sectional area, 9,to an end of which is connected by welding an end of the taperingportion 7 the cross-sectional area of which increases gradually toward aforward end of the bracing 5, as in for example a frustum of a cone orof a pyramid, and the portion having a larger cross-sectional area 6,which is joined by welding to the other end of the tapering portion 7.

The tapering portion 7 is secured in a portion thereof to the outerplate 11 of the column 3 by welding, and a forward end of the portionhaving a larger cross-sectional area 6 is joined by welding to apartition wall 12 provided in the interior of the column 3.

According to the above structuring, the connection portion 8 at whichconnected to each other are the tapering portion 7 and the portion of alarger cross-sectional area 6 is located in the interior of the column3, so that the stress from the side of the portion having a smallercross-sectional area 6, if occurred, can be dispersed into the outerplate 11 and the portion of a larger cross-sectional area 6, whereby astress concentration at the connection portion 8 can be avoided.

Further, the portion of a smaller cross-sectional area 9 and thetapering portion 7 of the bracing 5 are joined together at joiningportion 10.

The above construction of the joint portion of the column 3 and thebracing 5 can be variously modified, and FIG. 2 shows such a modifiedexample of the construction in which the outer plate 11 of the column 3is curved to be outwardly convex.

As shown in FIG. 3, further, the outer plate 11 of the column 3 mayotherwise be so curved as to be convex toward the inside of the column.Otherwise, the outer plate 11 of the column 3 may be V-shaped so as tobe outwardly convex as shown in FIG. 4 or to be convex toward the insideas shown in FIG. 5. The outer plate 11 may further otherwise be disposedat an inclination as shown in FIG. 6.

As shown in FIG. 7, further, it is also possible to make the bracingdevoid of the portion having a larger cross-sectional area 6 and thensecure the tapering portion 7 directly to the partition wall 12 insidethe column 3. As shown in FIG. 8, further, it may be devised to make thebracing 5 devoid of the portion of a larger cross-sectional area 6 andsecure the tapering portion 7 directly to the partition wall 12 withinthe column 3, and in addition, to curve the outer plate 11 of the column3 so as to be outwardly convex.

As shown in FIG. 9, further, the tapering portion 7 and the portionhaving a larger cross-sectional area 6 of the bracing 5 may be so madeas to have a face which coincides with the generatrix of the portionhaving a smaller cross-sectional area 9.

As shown in FIG. 10, further, it may be designed that the taperingportion 7 and the portion having a larger cross-sectional area 6 of thebracing 5 are made having a face which coincides with the generatrix ofthe portion having a smaller cross-sectional area 9 and that the outerplate 11 of the column is so shaped as to cross the portion having alarger cross-sectional area 6 and the tapering portion 7.

Further alternatively and as shown in FIG. 11, the tapering portion 7and the portion having a larger cross-sectional area 6 of the bracingmay be made having a face which coincides with the generatrix of theportion having a smaller cross-sectional area 9, and the outer plate 11of the column 3 is arranged to obliquely traverse the tapering portion7.

Lastly, as shown in FIG. 12, it may further alternatively be made tocurve the column 3 and arrange it to extend between the portion having alarger cross-sectional area 6 and the tapering portion 7.

We claim:
 1. In a marine structure which includes a platform, aplurality of hollow columns extending downward from said platform andeach having an outer member constituting an outer wall of said columnand a substantially planar partition wall secured within and directly tosaid outer member, said partition wall extending generallylongitudinally with respect to the axis of said column, and a bracingbeing adapted to connect adjacent two columns, each bracing comprising amiddle portion of relatively small uniform cross-section and a pair ofshort tapered portions at both ends thereof, an outer end of eachtapered portion being larger than an inner end thereof, wherein saidouter end of each short tapered portion is secured to said partitionwall within each column and an intermediate portion of each shorttapered portion is welded to said outer member of said column.
 2. Asemi-submerged marine structure according to claim 1, wherein an endportion of relatively large uniform cross-section is welded between saidend of each short tapered portion and said partition wall.
 3. Asemi-submerged marine structure according to claim 2, wherein saidtapered portion has a frusto-conical configuration.
 4. A semi-submergedmarine structure according to claim 1, wherein each of said shorttapered portions is welded directly to said partition wall.